1. Field of the Invention
Embodiments of the present invention are related to orthopaedic surgical devices, such as implants, and procedures using the implants. More particularly, embodiments of the present invention are directed to surgical devices involved in replacing, reconstructing or securing synthetic or biological connective tissue to a bone surface, such as, for example, attaching and maintaining a replacement anterior cruciate ligament (ACL) against a bone.
Embodiments of the present invention particularly relate to surgical implants manufactured of biocompatible (permanent or bioabsorbable) material, e.g., plastic, metal, or bioabsorbable (or biodegradable) polymer, copolymer, polymer alloy or composite and which implants are used for fixation of a synthetic or biological (connective tissue) graft into a drill-hole in a bone. Grafts according to the present invention include natural (auto- or allograft) and/or synthetic substitutes to ligament or tendon. Synthetic implants according to the present invention may be ceramic and/or polymeric and include fibrous braid implants or other implants comprised of fabric.
2. Description of Related Art
Reconstruction is the standard of care after anterior cruciate ligament (ACL) injury. In surgery it is generally known to use an autograft taken e.g., from the knee of the patient, to replace the ruptured ACL. The two most commonly used are the bone-patellar tendon bone (BPTB) and the hamstring tendon (semitendinosus tendon with or without gracilis tendon), although allografts, synthetic grafts and quadriceps tendon grafts have also been used as ACL substitutes. The surgical techniques of the ACL reconstruction using bone-tendon bone (BTB) graft and hamstring tendon graft are described in detail in the following references: Beck, C. L., Jr.; Paulos, L. E.; Rosenberg, T. D.: xe2x80x9cAnterior cruciate ligament reconstruction with the endoscopic technique,xe2x80x9d Operative Techniques in Orthopaedics, 2:96-98, 1992; Stxc3xa4helin, A. C.; Weiler, A.: xe2x80x9cAll-inside anterior cruciate ligament reconstruction using semitendinosus tendon and soft threaded biodegradable interference screw fixation,xe2x80x9d Arthroscopy, 13:773-779, 1997; Fu, F. H.; Ma, C. B.: Anterior Cruciate Ligament Reconstruction Using Quadruple Hamstring. Operative Techniques in Orthopaedics, 9:264-272, 1999. Additional references of interest include Hoffman, R. F. G.; Peine, R; Bail, H. J.; Sudkamp, N. P.; Weiler, A.: xe2x80x9cInitial fixation strength of modified patellar tendon grafts for anatomic fixation in anterior cruciate ligament reconstruction,xe2x80x9d Arthroscopy, 15:392-399, 1999.
In brief, the ruptured ACL is removed and drill-holes are made into the distal femur and proximal tibia into or into close vicinity of the original insertion sites of the ACL. The replacement substitute (graft) is harvested either from the patellar tendon (BTB) or from the semitendinosus- and gracilis muscle tendons (hamstring graft), pulled through the drill-holes to replace the ruptured ACL and finally fixed into these drill-holes, leaving the tendon part to act as a new ACL.
Rigid fixation of the ACL graft has been recognized as one of the most important factors that determine the long-term success of an ACL reconstruction (Kurosaka, M; Yoshiya, S; Andrish, J T: xe2x80x9cA biomechanical comparison of techniques of graft fixation in anterior cruciate ligament reconstruction, Am. J. Sports Med., 15:225-229, 1987; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000). Further, the tibial fixation of hamstring tendon grafts is considered more problematic than femoral fixation (Larson, R.: xe2x80x9cFixation techniques for hamstring and other soft tissue ACL grafts. The science: Comparative laboratory and clinical studies,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine p. 99-102, Orlando, Fla., Mar. 18, 2000; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000), mainly because the forces are subjected to the ACL substitute (graft) parallel with the tibial bone tunnel and the bone quality is substantially inferior in the tibia than in the femur.
Among the currently available soft tissue (hamstring) graft fixation implants, interference technique, in which the so called interference screw is inserted into the space between the drill-hole and the end of the graft to lock the graft into the drill-hole, is currently the most commonly used method to secure an ACL substitute to a bony drill-hole in an ACL reconstruction. The fixation screws, like interference screws, are normally made of metal, like stainless steel or titanium or of a bioabsorbable polymer, like polylactide. Metallic and/or bioabsorbable polymeric materials and composites suitable for manufacturing of fixation screws, are described in the literature (Vainionp{umlaut over (aa)}, S.; Rokkanen, P.; Txc3x6rmxc3xa4lxc3xa4, P.: xe2x80x9cSurgical Applications of Biodegradable Polymers in Human Tissues.xe2x80x9d Progr. Polym. Sci., 14:679-716, 1989; Weiler, A.; Hoffman, R. F. G.; Stahelin, A. C.; Helling, H. J.; Sudkamp, N. P.: Biodegradable Implants in Sports Medicine: The Biological Base. Current Concepts Arthroscopy 16:305-321, 2000).
During interference screw insertion, technical complications such as the threads of the screw damaging the graft or passing sutures, the graft rotating with the screw so that the optimal position of the graft is lost and/or the graft is damaged or the screw becomes inserted non parallel (divergent) to the graft thereby significantly decreasing the strength of fixation, often occur. There are also concerns specific to the metal interference screws. For example, in case of a need for revision surgery, metal screws can significantly complicate the operation, as the hardware inserted in the primary reconstruction has to be removed, sometimes resulting in considerable loss of bone in the fixation site, and thus, decreasing the strength of the fixation of the revised graft. In most severe cases, it may even be necessary to perform bone grafting prior to revision surgery (Brown, C. H.; Steiner, M. E.; Carson, E. W.: xe2x80x9cThe uses of hamstring tendons for anterior cruciate ligament reconstruction: Technique and results,xe2x80x9d Clin. Sports Med., 12:723-756, 1993; Schroeder, F. J.: xe2x80x9cReduction of femoral interference screw divergence during endoscopic anterior cruciate ligament reconstruction,xe2x80x9d Arthroscopy, 15:41-48, 1999). Metal screws have also been shown to disturb postoperative MRI evaluation (Shellock, F. G.; Mink, J. H.; Curtin, S.; Friedman, M. J.: xe2x80x9cMR imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact,xe2x80x9d J. Magn. Reson. Imaging, 2:225-228, 1992). The problems specific to metal screws can naturally be avoided by the use of screws made of bioabsorbable materials, but other problems arise, such as the bioabsorbable screw breaking during screw insertion. Also, the drill-hole has to be threaded for the insertion of the bioabsorbable screw, which not only delays surgical operation, but also increases trauma and removes mechanically stronger cortical bone, thus reducing the grip of the screw into the bone. Complications associated with the surgical technique, like those listed above, are also provided in the literature (Bach, B. R.: xe2x80x9cArthroscopy-assisted patellar tendon substitution for anterior cruciate ligament insufficiency,xe2x80x9d Am. J. Knee Surg., 2:3-20, 1989; Barber, A. F.; Buxton, E. F.; McGuire, D. A.; Paulos, L. E.: xe2x80x9cPreliminary results of an absorbable interference screw,xe2x80x9d Arthroscopy, 11:537-548, 1995; Matthews, L. S.; Soffer, S. R.: xe2x80x9cPitfalls in the use of interference screws for anterior cruciate ligament reconstruction: Brief report,xe2x80x9d Arthroscopy, 5:225-226, 1989; Matthews, L. S.; Lawrence, S. J.; Yahilo, M. A.; Sinclair, M. R.: xe2x80x9cFixation strength of patellar tendon-bone grafts,xe2x80x9d Arthroscopy, 9:76-81, 1993; Pierz, K.; Baltz, M.; Fulkerson, J.: xe2x80x9cThe effect of Kurosaka screw divergence on the holding strength of bone-tendon-bone grafts,xe2x80x9d Am. J. Sports Med., 23:332-335, 1995; Rupp, S.; Krauss, P. W.; Fritsch, E. W.: xe2x80x9cFixation strength of a biodegradable interference screw and a press-fit technique in anterior cruciate ligament reconstruction with a BPTB graft,xe2x80x9d Arthroscopy, 13:61-65, 1997; Safran, M. R.; Harner, C. D.: xe2x80x9cTechnical considerations of revision anterior cruciate ligament surgery,xe2x80x9d Clin. Orthop., 323:50-64, 1996).
Finally, although providing a possibility for a bioabsorbable and apertural (anatomic) fixation of the ACL substitutes and despite their adequate initial fixation strength in pull-out studies, interference technique has been shown to result in early slippage or even complete failure of the graft-anchor-bone complex during cyclic loading of hamstring grafts fixed interference screws (Giurea, M., Zorilla, P. Amis, A. A., Aichroth, P.: xe2x80x9cComparative Pull-Out and Cylic-Loading Strength Tests of Anchorage of Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 27: 621-25, 1999; Havig, M. T.; Paulos, L. E.; Weiss, J.; Ellis, B. S.; Bote, H.: xe2x80x9cInterference screw fixation of soft tissue ACL grafts: Effects of cyclic loading on initial fixation strength,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine, p. 28, Anaheim, Calif. Feb. 7, 1999; Van der Reis, W. L.; Deffner, K. T.; Rosenberg, T. D.: xe2x80x9cComparison of hamstring fixation devices under cyclic loading,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine, p. 88, Orlando, Fla., Mar. 18, 2000; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000).
Because of complications found in clinical use of interference screws, several attempts have been done to develop other types of anchoring devices for fixation of synthetic or natural ligaments or tendons in ACL reconstruction. For example, free tendon grafts can be fixed outside the drill-holes using either staples, screws and washers, so-called endobuttons, or tying sutures over buttons or screw posts.
Extra-articular or suspensory fixation methods, for example, methods that require fixation outside the bone tunnel such as is found with staples placed either on the anterior cortex of the tibia or implants with staples placed partially within an entrance opening of the tunnel, are another commonly used alternative to fix soft tissue grafts into bone drill-holes. Although these methods have been shown to provide superior fixation strengths to the interference technique, they require at least that a portion of the implant be exterior to the drill-hole. Further, in comparison to the apertural fixation methods, the stiffness of the suspensory methods has been shown to be clearly inferior (Ishibashi, Y; Rudy, T. W.; Livesay, G. A.; Stone, J. D.; Fu, F. H.; Woo, S. L.: xe2x80x9cThe effect of anterior cruciate ligament graft fixation site at the tibia on knee stability: Evaluation using a robotic testing system,xe2x80x9d Arthroscopy, 13:177-182, 1997). Suspensory or extra-articular fixation of grafts has also been accused of permitting micromotion of the individual tendons of the four-strand graft within the bone tunnel, which in turn, has been associated with the enlargement of the bone tunnels, increased AP-laxity and decreased stiffness of the reconstruction, possibly jeopardizing the success of the operation (Hoher, J., Moller, H. D., Fu, F. H. xe2x80x9cBone Tunnel Enlargement after Interior Cruciate Ligament Reconstruction: Fact or Fiction?xe2x80x9d Knee Surg. Sports Traumatol. Arthrosc. 6:231-240, 1998).
Crossbar or toggle fixators are the latest in the fixation implants developed to secure tendon graft in bone tunnel. In short, the basic principle of these implants is that the tendon(s) is/are looped over a crossbar/toggle-like structure placed in the bone drill-hole. To date, these devices have been designed for the femoral fixation of hamstring grafts, with two exceptions:
UK Pat Appl. GB 2 288 739 describes an anchor for anchoring a ligament or the like at or adjacent one end of a bone or channel in a bone, comprising a head portion and a near portion adapted to extend into the bone or channel and to receive the ligament. Even if this implant can be applied for fixation (anchoring) a ligament, it has the head portion which remains outside of the drill-hole on the surface of bone. This portion, located on bone surface, causes tension in soft-tissue on bone. This tension can cause irritation, pain and foreign body reactions (swelling or oedema) in soft tissue. The head portion may also be palpable below the skin, which is inconvenient for the patient. Further, this implant does not provide an anatomic fixation or enable the tensioning of the graft.
A more advanced version of the same principle has been described in GB 2,337,463, which is otherwise very similar to the device described in GB 2,288,739 except of having the means for holding the ligament under tension, and then, when appropriate tension is achieved, maintaining the desired tension by a locking means comprising of a crimpable washer and a lock nut. Although enabling the tensioning of the graft, this design is also not endosteal (intraboreal) and does not provide an anatomic fixation.
U.S. Pat. No. 5,632,748 describes an endosteal anchoring device for urging a ligament graft against a bone surface comprising an anchoring body, a member for resisting slippage of the anchoring body into the periphery of a bone tunnel under ligament tension, a member for avoiding puncturing, piercing or tearing of cross-fibers of the ligament graft and a member for urging the ligament graft flush against the inner surface of the bone tunnel for accelerated healing. This device can be located totally inside of the drill-hole of bone. However, this device is bulky because (a) the anchor member, (b) the ligament graft, which is encircled around the anchor member and positioned within the cross-sectional area of the groove on the anchor member and (c) the insertion member (which in combination with the anchor member provides a means of locking the ligament graft at a fixation site) all are located side by side inside of the drill-hole. Therefore a substantial amount of the drill-hole is filled with the device (anchor member+insertion member) and typically less than half of the space inside of drill-hole is left for the ligament graft, as can be seen from FIG. 1, FIG. 3, FIG. 6, FIG. 8 or FIG. 9 of U.S. Pat. No. 5,632,748. When the device is bulky in comparison to the ligament it means that a large amount of degradable foreign material is located near the ligament. Accordingly, the diameter of the drill-hole must be substantially larger than the diameter of the ligament. Also a large amount of foreign material means a large amount of polymer debris degrading in the vicinity of the ligament, resulting in an increasing risk for compromised healing of the ligament.
FI. Pat. No. 100217 B describes an implant for fixation of a tendon loop in ACL reconstruction. The implant comprises the first end which includes a hole through which a tendon has been slipped to form a loop and a transverse locking element for locking of the implant into the drill-hole inside of bone. The implant further comprises a base member which includes a fixation notch for inserting an installation instrument. Even if this fixation implant will be located totally inside of the drill-hole into the bone, the installation of the transverse locking element is difficult and causes the formation of additional trauma (wound into the soft tissues and an additional transverse hole into the bone)
U.S. Pat. No. 5,425,767 describes an anchor for an artificial ligament in a bone. The anchor comprises a Y-shaped socket having first and second arms angled with respect to each other. The first arm is sized to receive the ligament and has cross-grooves for gripping the ligament. A bullet shaped clamp element is rotatably mounted to the second arm. The clamp element also has grooves that directly contact the ligament to apply an oblique force against the ligament. The clamp element and cross-grooves in the first arm completely surround and compress the ligament to frictionally secure the ligament to the socket. This implant is bulky, because of the intersecting openings (the Y-shape) of the socket. Therefore the opening of the drill-hole in the bone must be significantly larger than the drill-hole deeper inside of bone. A larger drill-hole opening means increased trauma to the bone surface. Additionally the clamp element compresses the ligament, which may cause similar problems for the ligament as found with the fixation of a ligament with an interference screw.
U.S. Pat. No. 5,899,938 describes a graft ligament anchor comprising a graft ligament engagement member disposed in an opening in a bone, the graft ligament engagement member being arranged to receive a graft ligament alongside the engagement member, and a locking member for disposition in the opening, and at least in part engageable with the graft ligament engagement member. Movement of the locking member in the opening causes the locking member to urge the engagement member, and the graft ligament therewith, toward a wall of the opening to secure the graft ligament to the wall of the opening. Also in this case the compressing of the ligament may cause problems by damaging the ligament and/or by disturbing its nutrition and healing.
As illustrated by the foregoing summary, efforts are continuously being made to improve devices, instruments and surgical methods used in replacing and reconstructing torn or dislocated ligaments so as to make the process more efficient and effective. However, significant disadvantages still remain with all the presently known devices and methods offered by the prior art.
Accordingly it would be advantageous to overcome the disadvantages of the prior art and to design an implant for use in securing a transplant, such as a hamstring tendon graft, in a bone, such as a tibia, that would: (a) be bioabsorbable; (b) provide a rigid fixation of the transplant at the tunnel opening (apertural/anatomic fixation); (c) have no external hardware, i.e. the implant should be a completely intraboreal or endosteal design such that no part of the implant should protrude outside the bone drill-hole or be located on the outer surface of the tibia; (d) require no additional surgical trauma in addition to the single drill-hole in the tibia as would occur with additional drill-holes or additional skin incisions, etc.; (e) permit/provide a circumferential contact, i.e. ideally 360xc2x0 contact, between the transplant and bone drill-hole walls, and (f) enable tensioning of the transplant before it is secured into the drill-hole, e.g., by pulling the transplant/implant construct by hand.
Embodiments of the present invention are directed to implants that can be used to secure a graft or transplant, such as a tendon, to bone, and more particularly, within a hole that is drilled into bone, i.e. a so-called xe2x80x9cdrill-holexe2x80x9d. Drill-holes, according to the present invention, can be made into or through a bone. When the drill-hole is made through a bone, it has an entrance opening and a corresponding exit opening. In addition to its ordinary and accustomed meaning, the term xe2x80x9ctransplantxe2x80x9d includes according to specific embodiments an artificial or natural ligament or tendon graft that is used as a reconstruction material to replace a torn/injured ligament, e.g. an anterior cruciate ligament. The implants of the present invention may also be referred to herein as xe2x80x9canchorsxe2x80x9d as they anchor or secure the transplant to the bone. The anchors are designed to be placed completely within a drill-hole with no part of the anchor protruding beyond the surface of the bone adjacent to the opening of the drill-hole once it has been properly implanted. Stated differently, the anchor is absent from the surface of the bone after the implantation surgery.
The anchor of the present invention includes an anchoring member and a clamp member. The anchoring member includes an anchor element and a locking element connected to the anchor element, preferably in series relation. The anchor element is configured to retain the transplant such as by allowing the transplant to loop around the anchor element. According a certain embodiment of the invention, the anchor element may include a groove, hole or other opening through which the transplant may be slid or inserted and then looped around the anchor element. However, the anchor element may include a wide variety of other configurations to retain a transplant such as the anchor element being uni- or multi-compartmental and including a slot, a hole, a hook, one or more tabs or extensions or other types of a recess through or around which a transplant can be looped.
The portion of the anchor element forming the groove, hole or other opening has a surface area and is configured so as to allow the transplant to be looped without any substantial compression, crimping, cutting or other deleterious effect on the transplant. According to a certain embodiment, the surface area is smooth and free from structure which would abrade or otherwise damage the transplant. The transplant, when looped, is co-extensive with a portion of the length of the anchor element. The anchor element around which the transplant is looped advantageously serves to encourage contact between the wall of the drill-hole and the transplant, and in particular, at the intra-articular opening of the drill-hole, to facilitate healing and securing of the transplant to the bone. The anchor element around which the transplant is looped is configured so as to exclude excessive compression of the transplant against the wall of the drill-hole.
However, the transplant, when looped, is advantageously non-extending along the entire length of the anchoring member. That is, according to the present invention, the anchoring member is configured such that the transplant need not extend along the entire length of the anchoring member, but rather can be fixedly retained within a drill-hole by being looped around only a portion of the anchoring member, such as the anchor element, with the remaining portion of the anchoring member, such as the locking element, being free of transplant contact.
The locking element extends as one or more arms from the anchor element and, in certain embodiments of the invention, includes frictional elements that frictionally engage a wall of the drill-hole. Thus, the locking element serves to prevent the anchoring member from slipping out of the drill-hole. A clamp member is provided which engages the anchoring member to provide further frictional force between the anchoring member and the wall of the drill-hole and to further secure or xe2x80x9clockxe2x80x9d the anchoring member within the drill-hole. The clamp member is designed to engage the anchoring member within the drill-hole with no part of the clamp member protruding beyond the surface of the bone adjacent to the opening of the drill-hole. Stated differently, the clamp member, when fully engaged with the anchoring member once proper fixation has been achieved, is absent from the surface of the bone.
According to certain embodiments of the present invention, the locking element is generally cylindrical in design and has a width or diameter that is equal to or slightly less than the diameter of the drill-hole so as to provide for a snug fit of the anchoring member into the drill-hole while still facilitating ease of adjusting the anchoring member within the drill-hole. Although it can be, the diameter of the drill-hole need not be any larger than the width or diameter of the locking element because the transplant does not contact the locking element at a position where the locking element contacts the wall of the drill-hole. Also, the locking element itself may be fashioned from compressible materials allowing its insertion into a drill-hole having substantially the same diameter as the locking element.
According to certain embodiments of the present invention, the locking elements are free from transplant contact. The transplant is not present between the wall of the drill-hole and the locking elements, i.e. the locking elements make direct contact with the wall of the drill-hole. Since the transplant is coextensive with only a portion of the anchoring member, such as the anchor element, any contact between the transplant and degraded material from the anchoring member is advantageously minimized.
In view of the foregoing, it is an object of the present invention to provide an ACL reconstruction fixation implant or anchor for fixation of tendon or synthetic grafts inside of a drill-hole. The implant is safe and simple to insert into a drill-hole with minimal trauma.
Another object of the present invention is to provide a device which is manufactured of biocompatible (permanent or bioabsorbable) material, e.g., plastic, metal, or bioabsorbable (or biodegradable) polymer, copolymer, polymer alloy or fiber reinforced or particle filled bioabsorbable polymer composite, which implant could be inserted into a drill-hole made into a bone, to fixate an ACL graft into the drill-hole.
It is also an object of the present invention to provide an ACL reconstruction fixation device which has such a geometry that the implant slips easily into the drill-hole but expresses, when locked into the drill-hole, a strong resistance against slip-in or pull-out from the drill-hole.
It is another object of the present invention to provide a device for fixing an ACL graft into a bone, which does not interfere with non-invasive examinations (such as radiographs, MRI or CT), is biocompatible and results in/provides a strong and rigid fixation of a graft in ACL reconstruction.
Further, it is an object of the present invention to provide an ACL reconstruction fixation device that does not damage the graft and minimally disturbs the tissue metabolism and blood circulation, when located totally inside of a drill-hole in a bone so that no part of the implant protrudes the outer surface of the bone.
It is a still further object of the present invention to provide an ACL reconstruction fixation device which locks the tendon loop effectively inside of the drill-hole with minimal contact between the tendon and the device, thus enabling maximal filling of the drill-hole with the tendon substance and facilitating effective growth of tendon tissue to contact with the walls of the drill-hole.
It is also a still further object of the present invention to provide an ACL reconstruction fixation device which presses the individual (tendon) bundles of the graft firmly against the walls of the drill-hole at or near the intra-articular tunnel opening (apertural/anatomic fixation).
Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a permanent or bioabsorbable intraboreal (endosteal) graft fixation anchor for being simply and safely inserted into a hole or drill canal made into a bone, to securely fix a tendon graft (transplant) into the drill-hole, the anchor device comprising an anchoring member and a clamp member, the anchoring member including an anchor element for holding a loop of a transplant and a locking element to engage a clamp member in a manner to secure or lock the anchor within a drill-hole. The anchor device provides for the rigid fixation of the transplant against the walls of the drill-hole at or near the intra-articular tunnel opening to facilitate the healing of the transplant.